There are many different types of bicycles on the market today. For example, bicycles are available which have widely varying gear ratios, utilize materials ranging from steel to lightweight composites, and which include components tailored to match the rider's skill and expected use. Despite these differences, the underlying structure of most bicycles is essentially the same. A typical bicycle includes front and rear wheels rotatably mounted to a rigid frame, a seat disposed over a portion of the rear wheel and supported by the frame for supporting the rider, and handlebars connected through the frame to the front wheel for turning the bicycle. The bicycle is propelled by turning a chainwheel/sprocket mounted on an axle which rotates through a portion of the frame. The chainwheel/sprocket is linked to the rear wheel by a drive chain.
If a rider has one leg shorter than the other, it is difficult to get a proper fitting bicycle. The pedaling cadence or rhythm is also disturbed with resultant reductions in cycling power and speed. These reductions are particularly detrimental to the cycling performance of a racer. Prior attempts to compensate for the shorter leg and achieve smooth pedal motion have included the creation of orthopedic bike shoes and pedal lifts which effectively build up the shorter leg. In addition, riders have used spacer blocks, adjustable crank arms as described, for example, in U.S. Pat. No. 4,850,245, and pedals with various side plate heights.
These devices, generally, have affected the dynamics of the ride which is particularly unsatisfactory for the serious cyclist. For example, the cyclist can be forced to make a push/pull pedaling motion which feels clumsy and prevents efficient pedaling. Moreover, these devices often add weight to the rider or bicycle, making the devices less than desirable when optimal power and speed are desired. Thus, none of these devices has proven entirely satisfactory.
Accordingly, there has been a need for a novel bicycle crank and pedal assembly which compensates for a difference in the length of a rider's legs in order to permit smooth pedal motion. There is a further need for a crank and pedal assembly which can be easily customized for individual riders having a variety of leg length differences. Additionally, there is a need for a chain and pedal assembly wherein efficient pedaling cadence or rhythm can be maintained. Moreover, an assembly which equalizes the power or force between legs of different lengths is needed. The present invention fulfills these needs and provides other related advantages.